Device for pressure indication of an inflatible cuff

ABSTRACT

A device that indicates an internal pressure of an inflatable medical cuff. The device includes a membrane movable in response to a difference between an internal pressure of the device and an external pressure. The device includes a movable internal pressure indicator. The movable internal pressure indicator is operably associated with at least a portion of the membrane.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation-in-part of U.S. patent applicationSer. No. 10/515,950, filed Sep. 2, 2005, now pending, which isincorporated herein by reference in its entirety.

BACKGROUND

1. Technical Field

The present invention relates to a method and device for pressureindication. In particular, the invention relates to a method and devicefor indicating an air pressure of a cuff of a laryngeal mask or otherairway device.

2. Description of the Related Art

In 1988, Dr. Archie Brain invented a new airway device, called thelaryngeal mask, for delivering anesthetic gases and oxygen to anunconscious patient during an operation. Prior to this, patients werecommonly anaesthetized using an Endotrachial Tube running through thevocal cords of the patient into the trachea. Alternatively, a face maskconnected to a gas source was held over the patient's nose and mouth.

In use, the laryngeal mask is inserted into the pharangeal space(throat) deflated, and when correct positioning is observed, aninflatable cuff around the outside of the mask is inflated with airusing a syringe. The syringe is inserted into an end of a valve which isconnected to the cuff by a small tube, such that air passed through thevalve from the syringe is used to inflate the cuff. There are presentlyeight different sizes of the laryngeal mask available, and while allrequire different volumes of air to inflate the cuff, the maximumrecommended intra cuff pressure is 60 cm H₂O.

The Laryngeal Mask is now the preferred choice of anesthetists in manycountries, and its use continues to grow. The greater prevalence in useof the laryngeal mask has brought certain possible dangers to light. Dueto human errors and the possible diffusion of nitrous oxide into thesilicone cuff, the cuff may be excessively inflated. Such excessiveinflation of the cuff has the potential to damage nerves and tissuesaround the hypopharynx, and this potential danger has been the subjectof scientific papers in anesthesia journals.

In order to prevent over-inflation of the cuff, it is desirable to checkthe intra cuff pressure when the laryngeal mask is in place. Currently,the means for checking the air pressure of the cuff include a smallinflatable bulb in fluid communication with the cuff inflation tube. Toget an indication of the cuff pressure, medical personnel squeeze thebulb under slight pressure from their figures to thus subjectively judgethe intra cuff pressure. Alternatively, a manometer may be connected tothe cuff inflation valve in order to obtain an accurate pressuremeasurement. Manometers are, however, relatively expensive and somewhatbulky and can be inconvenient to connect to the cuff inflation valve asthe valve is usually close to the patient's mouth.

Similar problems can occur in other airway devices having an inflatablecuff, such as endotrachial tubes, for example.

BRIEF SUMMARY

At least one embodiment of the present disclosure may be summarized as adevice for indicating an internal pressure of an inflatable medicalcuff, comprising:

a membrane movable in response to a difference between said internalpressure and an external pressure; and

movable indication means operably associated with said membrane forindicating, in use of the device, said internal pressure.

In some embodiments, the internal fluid volume of the membrane is atatmospheric pressure, while the external fluid volume is at the internalcuff pressure. In some embodiments, the membrane is closed at one endand open to atmospheric pressure at the other end.

In some embodiments, the membrane and movable indicator are housed in ahollow body of the device. Preferably, the hollow body is at leastpartly transparent. Preferably, the hollow body is autoclavable andformed of one of polysulphone, Lexan (polyphalate carbonate) and Ultem(polyetherlmide). Alternatively, the device may be non-autoclavable anddisposable, in which case polyvinylchloride (PVC) can be used for someor all of the device materials. In some embodiments, the hollow body iscylindrical and has scale markings thereon with which a position of themovable indicator may be compared to indicate the internal cuffpressure.

The pressure indication device has distal and proximal ends, theproximal end being defined as the end of the device which is connectableto a cuff inflation tube, while the distal end is defined as beingopposite to the proximal end. In one embodiment, the proximal end has amale luer for providing a removable fluid connection to the cuffinflation tube. In another embodiment, the proximal end is directly andnon-removably connected to the cuff inflation tube.

In some embodiments, the distal end of the device is adapted to connectto a syringe. In one embodiment, the distal end includes a spring loadedvalve and a female luer and is arranged so that the valve is actuatedupon insertion of the syringe into the female luer, thereby opening thevalve and allowing fluid communication from or into the syringe into orfrom the device. In an alternative embodiment, a stopper valve is usedinstead of the spring loaded valve. The stopper valve operates toprovide a similar effect.

In some embodiments, the membrane is a bellows. Preferably, the bellowsis formed of silicone. In some embodiments, a wall thickness of thebellows is about 0.3 to 0.5 millimeters. More preferably, the thicknessis about 0.4 millimeters. Preferably, pleats of the bellows have anopening angle of about sixty degrees when the bellows is in a relaxedstate. In some embodiments, a flange is provided at the open end of thebellows for engaging a rebate in the proximal end of the device.Preferably, inner and outer chambers are defined by the membrane and thehollow body, where the inner chamber is the internal fluid volume of themembrane and the outer chamber is the external fluid volume bounded bythe hollow body on the outside and the membrane on the inside. In someembodiments, the outer chamber includes a substantially annular chamberbetween a wall of the hollow body and the membrane and an end chamberbetween the distal end of the device and the closed end of the membrane,the end chamber and annular chamber being separated by the movableindicator.

In some embodiments, the movable indicator is connected to the membraneat the closed end thereof. In some embodiments, the movable indicator isformed as a disk having a peripheral flange. In some embodiments, theflange has one or more channels therein for allowing fluid communicationbetween the end and the annular chambers. Alternatively, the channelsmay be provided in an inner part of the disk instead of the flange. Insome embodiments, the flange has an indication mark on an outsidesurface thereof, the mark being visible through said hollow member.Advantageously, the indication mark cooperates with markings on thehollow body to provide an indication of whether the cuff pressure is ata safe pressure.

In another aspect of the present disclosure, at least one embodiment maybe summarized as a bellows for use in a pressure indication device forinflatable medical cuff, the bellows having:

an open end and a closed end;

indication means disposed proximate said closed end for providing apressure indication;

said closed end being movable relative to said open end in response todifferential pressure between regions outside and inside of the bellows,such that said indication means is movable to indicate said differentialpressure.

In some embodiments, the inside region is at atmospheric pressure, whilethe outside region is at an internal cuff pressure of a cuff of alaryngeal mask. In some embodiments, the open end has a vent toatmospheric pressure. In some embodiments, the open end has a flangeconnectable to a bellows holding member. In some embodiments, theindication means includes a movable indicator connected to said closedend by connection means. In some embodiments, the connection meansincludes a boss formed on said closed end. In some embodiments, thebellows is formed of silicone, has a wall thickness of about 0.4millimeters and has pleats having an opening angle of about sixtydegrees in a relaxed state of the bellows.

In a further aspect of the present disclosure, at least one embodimentmay be summarized as a pressure responsive device, including:

a hollow body;

a membrane disposed within said hollow body and defining inner and outerchambers within said hollow body, the membrane being responsive todifferential pressure between said inner and outer chambers; and

a movable indicator disposed toward a closed end of the membrane, themovable indicator being visible through said hollow body for indicatingsaid differential pressure.

A still further aspect of the present disclosure, at least oneembodiment may be summarized as a method of determining an internalpressure of a cuff of a laryngeal mask or other airway device, includingproviding a pressure indication device at a cuff inflation tube of thelaryngeal mask or other airway device, the pressure indication devicehaving a membrane moveable in response to a difference between sideinternal pressure and an external pressure and a movable indicatoroperably associated with said membrane for indicating said internalpressure, and viewing said movable indicator to determine said internalpressure.

In some embodiments, if the determined internal pressure of the cuff isbelow a minimum level indicated on the pressure indication device, themethod further includes connecting a syringe to the pressure indicationdevice and injecting air into the cuff inflation tube from the syringethrough the pressure indication device. Alternatively, if the determinedinternal pressure of the cuff is above a maximum level indicated on thepressure indication device, the method further includes connecting asyringe to an end of the pressure indication device and withdrawing airfrom the cuff inflation tube through the pressure indication device intothe syringe. In some embodiments, following or during withdrawal orinjection of air from or into the cuff inflation tube, the methodfurther includes performing the viewing step again.

In another aspect, at least one embodiment provides a laryngeal maskhaving a pressure indication device as described above connectedthereto. In another aspect, at least one embodiment provides a laryngealmask having a pressure responsive device as described above connectedthereto.

In another aspect, at least one embodiment provides a method ofadministering a breathing gas to a patient, including locating a cuff ofa laryngeal mask adjacent a hypopharynx of a patient, the laryngeal maskhaving a pressure indication device as described above connected to acuff inflation tube of the laryngeal mask, inflating the cuff,determining an internal pressure of the cuff according to the methoddescribed above, adjusting the internal pressure of the cuff accordingto the determined cuff pressure, and administering the breathing gas tothe patient through the laryngeal mask.

The pressure indication device may advantageously be used with othermedical devices having an air-inflatable cuff, including for example,endotracheal tubes, laryngeal tubes, naso-tracheal tubes, univent tubesand combitudes. The pressure indication device is also applicable toairway management devices (AMDs) and Portex laryngeal masks.

Advantageously, the pressure indication device may be small and easilyconnected to, or integrally formed on the end of, the cuff inflationtube of the airway device so as to provide a simple and easilyreferenced indication of the internal cuff pressure. This means thatmedical personnel can easily obtain an objective measure of the cuffpressure without having to connect a manometer to the cuff inflationtube. The pressure indication device and methods of use therefor mayadvantageously reduce the incidence of damage to the hypopharynx area ofa patient due to over-inflation of the cuff of the laryngeal mask ordamage otherwise resulting from inadequate inflation or over-inflationof an inflatable medical cuff.

At least one embodiment may be summarized as a device for indicatinginternal pressure of an inflatable medical cuff including a hollowhousing having a first opening at one end thereof to which a cuffinflation tube can be coupled; a second opening at another end of thehousing to which a syringe can be coupled; a valve in the second openinghaving a valve element which can be unseated from sealing engagementwith a valve seat on coupling of the syringe to the second opening forpermitting inflating air from the syringe to pass into or from thehousing; a bellows having an open end and a closed end; the open end ofthe bellows being coupled to the housing at said first end and definingan inner chamber within the bellows and an outer chamber being definedbetween the bellows and the housing, and wherein the closed end of thebellows is disposed towards the other end of the housing; the housingincluding at least one vent which vents the inner chamber to atmosphere;and wherein the housing includes at least one fluid communicationpassage from the first opening to the outer chamber whereby in use theouter chamber is at the same pressure as the internal pressure of thecuff; whereby changes in internal pressure of the cuff cause expansionand retraction of the bellows such that the position of the closed endof the bellows indicates the internal pressure of the cuff. The hollowhousing may include a generally cylindrical body which is made fromtransparent material. The housing may include an integral end formationwhich includes said second opening. The housing may include an end bodywhich is coupled to the cylindrical body and may include said firstopening, said at least one communication passage and said at least onevent and wherein the open end of the bellows is connected to said endbody.

At least one embodiment may be summarized as a device for indicatinginternal pressure of an inflatable cuff including a housing having afirst opening to which an inflation cuff tube can be coupled; a secondopening to which a syringe can be coupled; a bellows having an open endin communication with an internal chamber; a cylindrical body portionmade of transparent material having means for mounting the bellowstherein for expansion and contraction in an axial direction of thebellows; and vents for venting the internal chamber to atmosphere, thearrangement being such that fluid pressure applied by the syringe in usecan cause compression and extension of the bellows to thereby indicatepressure within the housing wherein the axis of the housing is notaligned with an axis of the first opening or an axis of the secondopening.

At least one embodiment may be summarized as a device for indicatinginternal pressure of an inflatable medical cuff including a body havinga first inlet coupling having a first axis to which a cuff inflationtube can be connected, a second inlet coupling having a second axis towhich a syringe can be connected, the body including a transparenthousing which has a cylindrical chamber having a third axis therein, thecylindrical chamber being in fluid communication with the first andsecond inlet couplings; and a bellows located within the housing andhaving an internal chamber and being mounted at one end thereof so thata free end thereof is moveable relative to third axis in accordance witha pressure differential between the internal chamber and fluid admittedto the body through said first inlet coupling and wherein the third axisis not aligned with both of said first and second axes. The third axismay transverse to the first axis. The third axis may transverse to thesecond axis. The body may be formed from polycarbonate and the bellowsmay be formed from silicon rubber. The device may be disposable.

At least one embodiment may be summarized as a device that indicatesinternal pressure of an inflatable medical cuff including a hollowhousing of fixed length having a first generally closed end and anopposed second generally closed end and a generally hollow cylindricalbody extending between the opposed generally closed ends, the generallyhollow cylindrical body is made from transparent material, the hollowhousing having a first opening configured to couple with a cuffinflation tube, a second opening configured to couple with a syringe,and at least one vent extending from an exterior surface of the hollowhousing to an interior of the hollow housing, the at least one ventbeing proximal to the first generally closed end of the pair of opposedgenerally closed ends; a valve in the second opening having a valveelement which can be unseated from sealing engagement with a valve seaton coupling of the syringe to the second opening for permittinginflating fluid from the syringe to pass into or from the hollowhousing; and a bellows having an outer surface and an open end in fluidcommunication with an inner chamber and a closed end, the bellowsextending into the interior of the hollow housing with the open end ofthe bellows coupled to the hollow housing at the first generally closedend of the pair of opposed generally closed ends, the inner chamber ofthe bellows in fluid communication with an atmosphere that is externalto the device via the at least one vent, wherein an outer chamberextends between the outer surface of the bellows and the hollow housing,and wherein the first opening and the second opening are in fluidcommunication with the outer chamber, whereby in use the outer chamberis at a pressure that is the same as an internal pressure of a cuffcoupled to the first opening, whereby changes in the internal pressureof the cuff cause expansion and retraction of the bellows such that aposition of the closed end of the bellows indicates the internalpressure of the cuff. The hollow housing may have at least one fluidcommunication passage from the first opening to the outer chamber. Atleast one of the pair of opposed generally closed ends may be integralwith the generally hollow cylindrical body of the hollow housing. The atleast one vent may extend through a portion of the generally hollowcylindrical body. The at least one vent may extend through a portion ofthe first generally closed end of the pair of opposed generally closedends. The first opening may be at the first generally closed end or thesecond generally closed end the pair of opposed generally closed ends,and wherein the second opening may be at the other one of the pair ofopposed generally closed ends. The first opening and the second openingmay be at the same generally closed end of the pair of opposed generallyclosed ends. The generally hollow cylindrical body may define alongitudinal axis, wherein the first opening may define a first axis,wherein the second opening may define a second axis, and wherein atleast one of the first axis and the second axis may not be aligned withthe longitudinal axis. The first axis and the second axis may berespectively aligned generally transverse to the longitudinal axis. Thefirst axis may aligned generally transverse to the longitudinal axis,and the second axis may be aligned generally parallel to thelongitudinal axis. The generally hollow cylindrical body may define alongitudinal axis having the bellows generally aligned therewith,wherein the closed end of the bellows may be biasable along thelongitudinal axis by a fluid in the outer chamber.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

In the drawings, identical reference numbers identify similar elementsor acts. The sizes and relative positions of elements in the drawingsare not necessarily drawn to scale. For example, the shapes of variouselements and angles are not drawn to scale, and some of these elementsare arbitrarily enlarged and positioned to improve drawing legibility.Further, the particular shapes of the elements as drawn, are notintended to convey any information regarding the actual shape of theparticular elements, and have been solely selected for ease ofrecognition in the drawings.

FIG. 1 is a side cross-sectional view of a pressure indication deviceaccording to one non-limiting illustrated embodiment;

FIG. 2 is an end view of an indicator plate for use in the indicationdevice shown in FIG. 1 according to one non-limiting illustratedembodiment;

FIG. 3 is a side view of the indication device of FIG. 1, showingexample markings on the outside of the device, according to onenon-limiting illustrated embodiment;

FIG. 4 illustrates an example of use of a pressure indication device ofan embodiment of the invention with a cuff inflation line and a syringeaccording to one non-limiting illustrated embodiment;

FIG. 5 is a side cross-sectional view of a bellows according to onenon-limiting illustrated embodiment;

FIG. 6 is a side cross-sectional view of a pressure indication device ofanother non-limiting illustrated embodiment;

FIG. 7 is an illustration of a laryngeal mask having the pressureindication device shown in FIG. 6 non-limiting illustrated embodiment;

FIG. 8 is a side cross-sectional view of a pressure indication deviceaccording to a further non-limiting illustrated embodiment;

FIG. 9 is a side cross-sectional view of a bellows according to afurther non-limiting illustrated embodiment;

FIG. 10A is an end side cross-sectional view of a hollow tube for use inthe pressure indication device according to one non-limiting illustratedembodiment;

FIG. 10B is an isometric view of the hollow body of FIG. 10A accordingto one non-limiting illustrated embodiment;

FIG. 11A is an isometric view of a male end of the pressure indicationdevice shown in FIG. 8; according to one non-limiting illustratedembodiment FIG. 11B is an end view of the male end shown in FIG. 11Aaccording to one non-limiting illustrated embodiment;

FIG. 11C is a cross-section view taken along lines B-B of the male endshown in FIG. 11B according to one non-limiting illustrated embodiment;

FIG. 11D is a side view of the male end shown in FIG. 11A according toone non-limiting illustrated embodiment;

FIG. 11E is a side cross-sectional view of the male end shown in FIG.11D, taken along the lines A-A according to one non-limiting illustratedembodiment;

FIG. 12A is an isometric view of a valve plate used in the pressureindication device shown in FIG. 8 according to one non-limitingillustrated embodiment;

FIG. 12B is an end view of the valve plate shown in FIG. 12A accordingto one non-limiting illustrated embodiment;

FIG. 12C is a side cross-sectional view of the valve plate shown in FIG.12B, taken along the lines A-A according to one non-limiting illustratedembodiment;

FIG. 13 is an end view of a stopper used in the pressure indicationdevice shown in FIG. 8 according to one non-limiting illustratedembodiment;

FIG. 14 is a partial cross-sectional side view of a female end of thepressure indication device of FIG. 8, illustrating the stopper in acompressed state whereby fluid communication is enabled;

FIG. 15 is an enlarged cross-sectional view according to onenon-limiting illustrated embodiment;

FIG. 16 is an enlarged cross-sectional view according to anothernon-limiting illustrated embodiment; and

FIG. 17 is an enlarged cross-sectional view according to anothernon-limiting illustrated embodiment.

Embodiments are hereinafter described, by way of example only withreference to the accompanying drawings.

DETAILED DESCRIPTION

In the following description, certain specific details are set forth inorder to provide a thorough understanding of various disclosedembodiments. However, one skilled in the relevant art will recognizethat embodiments may be practiced without one or more of these specificdetails, or with other methods, components, materials, etc. In otherinstances, well-known structures associated with _cuffs have not beenshown or described in detail to avoid unnecessarily obscuringdescriptions of the embodiments.

Unless the context requires otherwise, throughout the specification andclaims which follow, the word “comprise” and variations thereof, suchas, “comprises” and “comprising” are to be construed in an open,inclusive sense, that is as “including, but not limited to.”

Reference throughout this specification to “one embodiment” or “anembodiment” means that a particular feature, structure or characteristicdescribed in connection with the embodiment is included in at least oneembodiment. Thus, the appearances of the phrases “in one embodiment” or“in an embodiment” in various places throughout this specification arenot necessarily all referring to the same embodiment. Further more, theparticular features, structures, or characteristics may be combined inany suitable manner in one or more embodiments.

As used in this specification and the appended claims, the singularforms “a,” “an,” and “the” include plural referents unless the contentclearly dictates otherwise. It should also be noted that the term “or”is generally employed in its sense including “and/or” unless the contentclearly dictates otherwise.

The headings and Abstract of the Disclosure provided herein are forconvenience only and do not interpret the scope or meaning of theembodiments.

Embodiments are described hereinafter generally in relation to theirapplicability to laryngeal masks. It should be understood, however, thatembodiments are also applicable to other applications requiringpressure, indications of a similar magnitude and to other airway deviceshaving air-inflatable cuffs, such as some endotrachial tubes.

Referring to FIG. 1, one embodiment relates to a pressure indicatordevice 10 having a cylindrical outer wall 12, a bellows 14 and femaleand male generally closed ends 16, 17 (also referred to as the distaland proximal ends, respectively). The bellows 14 is located inside theouter wall 12 and moves concentrically therewithin in response todifferential pressure. One end of the bellows 14 is attached to the maleend 17, while the other end of the bellows, in its relaxed state,extends towards the female end 16. At the male end 17, the bellows isopen to atmospheric pressure via a vent passage 30, while the other endof the bellows 14 is closed and has a boss 19 disposed thereon. The boss19 engages a hole 39 in an indicator 38 connected to the bellows 14 atthe closed end thereof. The vent passage 30 extends from an exteriorsurface of the pressure indicator device 10 to an interior of thepressure indicator device 10 and allows fluid communication between aportion of the interior of the pressure indicator device 10 and anatmosphere external to the pressure indicator device 10. The ventpassage 30 may extend through a portion of the male generally closed end17.

The outer wall 12 is formed of polysulphone or alternatively anothersubstantially clear autoclavable material such as Lexan (polyphalatecarbonate) and Ultem (polyetherlmide). The outer diameter of the outerwall 12 is preferably between about 9 millimeters and 15 millimeters andideally about 12.8 millimeters (which is about 0.5 inches). The clarityof the outer wall 12 allows the position of the indicator 38 to be seenthrough the outer wall 12. The length of the device 10 is preferably inthe order of about 40 mm total, although this may vary somewhat,depending on requirements. The length of the device 10 is normallyfixed, and the device 10 is normally rigid.

The location of the bellows 14 within the outer wall 12 and the femaleand male generally closed ends 16, 17 serve to define an inner chamber34 within the bellows 14, which is at atmospheric pressure due to thevent passage 30, and an outer chamber 32 defined by the roughly annularspace between the bellows 14 and the outer wall 12 and between theclosed end of the bellows 14 and the female generally closed end 16.This outer chamber 32 is in fluid communication with the cuff inflationline through a male luer outlet passage 31 so that, in use of theindicator device 10, the outer chamber 32 is at the same pressure as thecuff of the laryngeal mask and the inner chamber 34 is at atmosphericpressure. This differential pressure causes the bellows 14 to contractfrom its elongated relaxed state, thereby moving the indicator 38. Thebellows 14 is calibrated so as to consistently contract or compress tothe same degree in response to the same cuff pressure.

The indicator 38 has a runner 18 which has a substantially parallelsurface to that of the interior surface of the outer wall 12 so as tokeep an indication mark 43 (which runs circumferentially around theoutside of the runner 18) substantially perpendicular to the directionof travel of the bellows along an axial center of the indicator device10 and to keep the movement of the bellows 14 substantially axiallycentered. As shown in FIG. 2, the indicator 38 is formed of a circulardisk 42 with the runner 18 constituting a peripheral annular flangeextending perpendicularly to the plane of the plate in both directions.The plate 42 has the hole 39 in the center thereof for receiving boss 19in order to attach the indicator 38 to the bellows 14. A suitableadhesive may be used as well as, or instead of, the mechanicalconnection of the boss 19 and hole 39. The runner 18 has a number ofchannels 41 in its outer surface extending in the axial direction of theindication device 10 for allowing fluid communication from an endchamber 36 adjacent to the female end 16 with the annular part of outerchamber 32 bounded by the outer wall 12 on the outside and the pleats ofthe bellows 14 on the inside. As an alternative to the channels 41 beingformed on the outside of the runner 18, they may be formed in the plate42 towards an outer circumference thereof, but not so central as to beblocked by the end of the bellows 14 adjacent to the boss 19.

The runner 18 effectively provides a means of stabilizing the axialmovement of the bellows under compression or relaxation. Otherstabilizing means may be provided, however, such as a pin attached atthe closed end of the bellows 14 in place of boss 19 and extendingaxially within a fixed guiding sheath anchored toward or at the femaleend.

The male end 17 of the indication device 10 is formed so as to providethe vent passage 30 to the inside of the bellows 14 and an outletpassage 31 for connection to the cuff inflation line. The male end 17 isformed as a male luer fitting 26, having the outlet passage 31 at thecenter thereof, an outer male luer wall 28 and a female luer thread 29on the inside of the luer wall 28 for engaging a male thread of a femaleluer fitting, if necessary. The male end 17 also has a circular rebate27 for receiving an end flange 56 (shown in FIG. 5) of the bellows 14.The end flange 56 is secured in the rebate 27 by a suitable adhesive forproviding an air tight seal under pressures in the order of 60 cm H₂O.

The male end 17 is, in the embodiment pictured in FIG. 1, formedseparately to the outer wall 12. However, an alternative embodimentprovides that the male end 17 be formed integrally with the outer wall12, in which case the axial orientation of the bellows 14 is reversedand the vent passage 30 and rebates 27 are provided in an altered femaleend 16. Similarly, the embodiment shown in FIG. 1 illustrates that thefemale end 16 is formed separately to the outer wall 12, but in analternative embodiment, these are formed integrally, without the needfor joining the two portions with adhesives. In some embodiments, themale end 17 is formed separately to the outer wall 12 but has thebellows 14 attached thereto during assembly, while the outer wall 12 andfemale end 16 are formed integrally and are placed over the bellows 14and adhered to the male end 17 by suitable adhesives such an alternativeembodiment is shown, for example in FIG. 8. Regardless of whether theouter wall 12 is formed integrally with the male and/or female end 17,16, the axial orientation of the bellows 14 may be reversed (e.g., sothat the open end of the bellows 14 is connected to the female end 16 ona rebate suitably formed therein and the closed end extends towards themale end 17).

The female end 16 has a spring-loaded stop valve 20 housed therein whichis normally closed to seal off the outer chamber 32 (including endchamber 36) at the female end 16. The valve 20 can be opened in responseto depression of a valve actuator 21 against the action of a spring 23.Once the actuator 21 is released, the spring 23 acts against theactuator 21 to return it to its normal extended position and hence closethe valve 20. The actuator 21 extends within a female luer fitting 22whereby, when a male luer fitting is inserted into the female luerfitting 22, the actuator 21 is depressed, thus opening the valve 20.This would occur if, for example, a male luer fitting on the end of asyringe were inserted into the female luer fitting 22. With the actuator21 depressed, the valve 20 is opened and air from the syringe can beinjected into the outer chamber 32. The female luer fitting 22 isprovided with female luer bosses 24 for engagement with a male luerthread, such as that shown on syringe 70 in FIG. 4 by reference numeral74.

Referring now to FIG. 3, the pressure indication device 10 has anindication region 44 around the circumference of the outer wall 12 forproviding a scale against which to compare the position of the indicator38. The indication region 44 includes an over-pressure band 46 and anat-pressure band 48. The over-pressure band 46 has an upper indicationbound 45 defining the upper bound of the indication region 44 andover-pressure band 46. A maximum pressure line 47 separates theover-pressure band 46 from the at-pressure band 48, the maximum pressureline 47 corresponding to an intra cuff pressure of 60 cm H₂O. Theat-pressure band 48 has a lower indication bound 49, below which thecorresponding intra cuff pressure is considered sub-optimal. Theat-pressure band 48 represents a range of pressures below the maximumpressure of 60 cm H₂O which are considered to be within an optimal intracuff pressure range, such that when the indicator 38 is visible in theat-pressure band 48, the cuff pressure does not need to be altered. Ifthe indicator 38 is visible above the maximum pressure line 47, airshould be withdrawn from the cuff until the indicator 38 enters theat-pressure band 48. If the indicator 38 is visible beyond the upperindication bound 45, this indicates extreme over-pressure of the cuff,and the cuff pressure should be reduced immediately. In someembodiments, the over-pressure band 46 is lightly colored in red, whilethe at-pressure band 48 is lightly colored in green, with the indicatormark 43 of the indicator 38 being visible through the outer wall 12 as ablack line circumferentially running around the outside of the runner18. The coloring of the over-pressure band 46 and at-pressure band 48should not be so dark as to obscure the visibility of the indicator mark43. The at-pressure band 48 may, for example represent pressures between55 and 60 cm H₂O, while the over-pressure band 46 may representpressures between, say, 60 and 64 cm H₂O. Other pressure ranges may beappropriate for airway devices other than the laryngeal mask.

Referring now to FIG. 4, an illustration of use of the pressureindication device 10 is described. The male luer fitting 26 isinsertable into the standard female luer fitting of a cuff inflationline 60. The cuff inflation line 60 has an inflation valve 61 housingthe female luer fitting, a cuff pressure indicator balloon 62 connectedto the inflation valve 61 on the cuff side thereof and a cuff inflationtube 64 connecting the cuff (not shown) with the cuff pressure indicatorballoon 62.

When the pressure indication device 10 is fitted onto the cuff inflationline 60 by inserting the male luer fitting 26 into the female luerfitting of the inflation valve 61, the inflation valve 61 is actuated(opened). This then provides fluid communication from the cuff inflationtube 64 through to the outer chamber 32 of the pressure indicationdevice 10, whereupon, if the cuff pressure is greater than atmospheric,the bellows 14 will be compressed due to the pressure difference,resulting in visible movement of the indicator 38 within or relative tothe indication region 44. Relevant medical personnel can then read therelative pressure within the cuff from the position of the indicator 38within or relative to the indication region 44.

If the position of the indicator 38 relative to the indication region 44indicates that the cuff pressure is too great or too small, the medicalpersonnel can then withdraw or inject air from or into the cuff by usinga syringe 70. This is done by inserting a male luer 72 of the syringe 70into the female luer fitting 22 of the pressure indication device 10 andtwisting the syringe 70 so as to engage the male luer thread 74 with thefemale luer bosses 24. The insertion of the syringe male luer 72 intothe female luer fitting 22 actuates the valve 20 and thereby allows airto be withdrawn or injected from or into the outer chamber 32 (via endchamber 36) and thence from or into the cuff inflation line 60. Theinjection or withdrawal of air is performed by movement of a plunger 76within the syringe 70. This plunger 76 seals an end chamber 78 in theend of the syringe 70 so as to maintain the pressure in the cuffinflation line 60 during the cuff pressure adjustment.

While adjusting the air pressure in the cuff, the medical personnelmonitor the position of the indicator 38 relative to the indicationregion 44 so as to ensure optimal cuff pressure is obtained (i.e., bylocating the indicator 38 within the at-pressure band 48). Thus, thepressure indication device 10 advantageously allows an initial check ofthe internal cuff pressure, subsequent adjustment of the cuff pressureusing a syringe and continuous cuff pressure monitoring during and afteruse of the syringe 70. This is a better and more objective means ofdetermining the cuff pressure than by manually finger-squeezing the cuffpressure indicator balloon or by periodically or sequentially takingpressure measurements with a manometer, which involves detaching themanometer and attaching a syringe each time the cuff pressure needs tobe adjusted.

Shown in FIG. 5 is an embodiment of the bellows 14 in a relaxed state.The bellows 14 has an inner surface 103 and an outer surface 105. Thebellows 14 is formed of silicone and has a wall thickness, w, of about0.3 to 0.5 millimeters, but preferably closer to 0.3 millimeters,between the inner surface 103 and outer surface 105. The thickness ofthe bellows is greater however, at a closed end 54 where the boss 19 islocated and may be slightly increased at the flange 56 at its open end52. The open end 52 extends to a generally open interior 134 defined bythe inner surface 103.

In its relaxed state, the length of the bellows 14 is about 28millimeters and pleats of the bellows 14 open at an angle, N, of aboutsixty degrees. The inner diameter, x, of the bellows 14 is preferred tobe about 5 millimeters, and is more preferably about 4.9 millimeters. Anouter diameter, y, of the bellows 14 is preferred to be about 9.6millimeters, and more preferably 9.62 millimeters. The precisedimensions, thickness, length, opening angle, number of pleats andconfiguration of the bellows may be subject to some variation whilestill being capable of performing operably. The silicone bellows 14 ispreferably formed of silicone rubber having shore hardness A 40 to 60.Depending on the shore hardness of the bellows 14, the location of theindication region 44 on the outer wall 12 will vary in proximity to theproximal and distal ends of the indication device 10. The preciselocation of the indication region 44 and maximum pressure line 47 isdetermined by calibration using a manometer.

FIG. 6 illustrates an alternative embodiment of the pressure indicationdevice, represented by reference numeral 110. The pressure indicationdevice 110 is substantially the same as the embodiment shown in FIG. 1and designated by reference numeral 10, except that it is intended forpermanent connection to the cuff inflation tube 64 in place of theinflation valve 61 and cuff pressure indicator balloon 62. Likereference numerals in FIG. 6 represent like features and the precedingdescription of those features applies to this embodiment.

In pressure indication device 110, a male end 117 is provided without amale luer fitting but instead having an outlet 128 to which the cuffinflation tube 64 is connected (for example, by suitable adhesives), andthe outer chamber 32 is then placed in fluid communication with the cuffinflation tube 64 through outlet passage 131. Instead of having aprotruding tubular outlet 128 such as that illustrated in FIG. 6, thecuff inflation tube 64 may otherwise be fixed to the male end 117 so asto be in fluid communication with the outer chamber 32.

Advantageously, the pressure indication device 110 is assembled as partof a laryngeal mask assembly 125 (see FIG. 7) so as to replace the cuffpressure indicator balloon and inflation valve 62, 61 and obviate theneed to connect and disconnect the pressure indication device 10 to thecuff inflation line 60 of the laryngeal mask. The pressure indicationdevice 110 is intended to be fitted to a reusable laryngeal mask orother airway device and must therefore be autoclavable. Advantageously,the materials selected for the device 110 (and 10) are all autoclavable.

An example of a laryngeal mask having the pressure indication device 110assembled as part thereof is shown in FIG. 7, designated by referencenumeral 125. FIG. 7 shows the pressure indication device 110 connectedat the end of cuff inflation tube 64, which is in-turn connected to thecuff 120.

Referring now to FIGS. 8 to 14, a further embodiment of the pressureindication device is shown, designated by reference numeral 210. Thisembodiment is similar to the previously described embodiments in manyrespects, including, for example, its functional interaction with thecuff inflation tube and syringe and in having markings on itscylindrical body for facilitating the pressure indication function. Thisembodiment is different, however, in that a different embodiment of thebellows is employed, together with modified female and male ends. Forpurposes of clarity and ease of understanding, the following descriptionof this further embodiment will focus on functional differences betweenthis embodiment and the previously described embodiments. Wheredifferent features are not mentioned, this implies that the relevantfunctional features are the same or similar between the embodiments.

Referring to FIG. 8 specifically, pressure indicator device 210 has anouter wall 212 for housing a bellows 214 and has a male end 217 andoppositely disposed female end 216. The bellows 214 is affixed by asuitable adhesive to a rebate portion 227 of the male end 217 and themale end 217 is fixed similarly to the outer wall 212. Materials used inthis embodiment are generally the same as those used in the embodimentspreviously described and thus the adhesives chosen to affix the bellows214 to the male end 217 and the male end 217 in turn to the outer wall212 should therefore be suitable for adhering (for example) silicone toLexan and Lexan to Lexan, respectively. In this embodiment, the outerwall of female end 216 is integrally formed with outer wall 212. Fromouter wall 212, female end 216 tapers frustoconically toward an endopening 226. Apart from being fixed to the male end 217, the bellows 214is moveable longitudinally within the body of the device 210 in responseto a pressure difference between inner chamber 234 and outer chamber232. The inner chamber 234 is bounded by the inside walls of the bellows214 and the male end 217 but is vented to atmosphere through atmosphericvent passages 230 in the male end 217.

The outer chamber 232 is bounded by the outer wall 212 and the outersurface of the bellows 214. The outer wall 212 has a number of internalwall ribs 213 (better illustrated in FIGS. 10A and 10B) which protrudefrom the internal wall surface of outer wall 212 by about 0.25 mm. Theseinternal wall ribs 213 serve to act as a guiding means for stabilizingthe bellows 214 as it moves within the outer wall 212. Between theinternal wall ribs 213 there is an interrupted annular gap through whichfluid may communicate past the largest diameter pleats (describedfurther below) of the bellows 214.

An outlet passage 231 in the male end 217 has an outlet fluidcommunication channel 240 (shown in FIGS. 11A, 11D and 11E) whichcommunicates with the outer chamber 232 so as to place the outer chamber232 at the internal cuff pressure when the male end of the device 210 isfitted to the cuff inflation tube. At the other end of the device 210,the outer chamber 232 includes a female end chamber 236 whichcommunicates through the female end 216 to a syringe when valve 220 isactuated.

Valve 220 includes a valve support plate 219 seated against the end ofthe internal wall ribs 213 and supporting a valve stopper 221. The valvestopper 221 is generally hemispherical and hollowed and somewhatcup-shaped, with a concave face facing toward the bellows 214. Thestopper 221 has a head portion 223 disposed on its outer convex face forfitting into and loosely engaging the female end opening 226. In itsrelaxed state, the stopper 221 sits against the inside wall of thefemale end 216 adjacent the female end opening 226. This interior wallportion contacted by the stopper is generally frustoconical such that,when the outer convex surface of the stopper 221 sits against thatportion of the interior wall of the female end 216, female end opening226 is occluded. Even in its relaxed state, the stopper 221 is stillslightly compressed between the frustoconical interior wall of femaleend 216 and the valve support 219 so as to seal the valve 220. Thestopper 221 rests, at its bottom or outer annular edge, against astopper support flange 228 (shown in FIGS. 12A, 12B and 12C).

The stopper 221 has a channel or notch 224 formed in its head portion223. This channel 224 allows passage of fluid from the syringe aroundthe head portion 223 and into the female end 216 when the stopper 221 isdepressed by the syringe nozzle (in its compressed state), as shown inFIG. 14. With reference also to FIG. 14, when the stopper 221 isdepressed by the insertion of the syringe nozzle 72 into the female endopening 226, the outer convex surface of the stopper 221 adjacent headportion 223 is moved away from the interior frustoconical wall of femaleend 216, leaving a gap therebetween. Also, as head portion 223 does notitself occlude the female end opening 226, but rather leaves a smallgap, this allows fluid to flow from the syringe nozzle 72 through thehead channel 224, around the head portion 223 and through the gapcreated between the outer convex wall of the stopper 221 and theinterior frustoconical wall of the female end 216. The fluid is thenfree to flow through female end fluid channels 222 in the valve supportplate 219. The female end fluid channels 222 are formed as a number, forexample 4, of holes formed toward a radially outer peripheral area ofthe valve support plate 219 (as shown in FIGS. 12A, 12B and 12C). Thedirection of fluid flow into female end 216 from syringe head 72 isdepicted in FIG. 14 by small arrows. Fluid may flow similarly in theother direction in response to suction from the syringe when the stopperis compressed.

The valve support plate 219 has a center hole 225 in the center thereofin communication with the concave underside of stopper 221. Center hole225 serves to prevent a vacuum forming inside the stopper 221 after itis compressed. Such a vacuum would hinder the stopper 221 from returningits relaxed state and would thus impair the function of valve 220. Ascan be appreciated from the described arrangement, the natural state ofvalve 220 is closed, due to the tendency of the flexible stopper 221 toreturn to its relaxed state, by which it occludes female end opening226. To accomplish this, the stopper 221 is preferably formed ofsilicone rubber and has a minimum shore hardness A60.

FIG. 9 shows a cross-sectional representation of bellows 214 (in itsrelaxed state) of a roughly cylindrical form, for use in the pressureindication device 210. The bellows 214 may alternatively be employed inother embodiments of the pressure indication device, providing thoseembodiments have internal wall ribs 213 for guiding and stabilizing themovement of the bellows as it contracts or expands within the device. Inthis embodiment the bellows 214 is defined by an inner surface 203 andan outer surface 205. The inner surface 203 defines an open interior235. The bellows 214 includes an open end 252 in fluid communicationwith the open interior 235 and a closed end 254. The closed end portion254 is modified somewhat relative to the previously describedembodiment. The closed end 254 does not have a boss formed on its end.The indication mark is not provided on a flange connected to the closedend, but is instead formed on an outer annular edge of the last pleattoward the closed end 254. The indication marks are shown in FIGS. 8 and9 and designated by reference numeral 238. These indication marks may beformed as a paint or dye applied to the bellows 214 after it is molded.This paint or dye must contrast with the color of the material used forthe bellows. For example, if the bellows is formed of a white orgenerally translucent material, the indicator mark 238 should be of acontrasting dark color. In this embodiment, as there is no disk andflange to guide movement of the bellows within the outer wall 212, thisguiding and stabilizing function is performed by larger diameter pleats260 (including the end pleat on which indicator marks 238 are formed),in cooperation with the internal wall ribs 213. In the embodiment of thebellows 214 shown in FIG. 9, the last and third-from-last pleats in thebellows are enlarged so as to contact the internal wall ribs 213 as theymove longitudinally within the device 210. This stabilization isimportant so that the orientation of the indication mark relative to thescale markings on the outside of the outer wall 212 is not skewed duringcompression of the bellows 214, which may lead to an inaccurate pressurereading. Additionally, thickened portions 239 are provided between thelast three pleats toward the closed end 254 to stiffen the end part ofthe bellows 214. This stiffening assists in stabilizing the travel ofthe bellows and thus the indication mark. The thickened portions 239also serve to minimize movement of the last pleat on which theindication mark 238 is formed relative to other pleats duringcompression of the bellows 214, thus assisting in calibration of thedevice for serving its pressure indication function. These thickenedportions 239 may be formed around the circumference of the bellows 214in the relevant pleat position or may be formed as circumferentiallyspaced ribs connecting the pleats at a number of points for stiffeningthereof.

As shown in FIG. 9, the outer diameter of smaller pleats 258, indicatedby a, is less than the outer diameter of the larger diameter pleats 260,represented by b. The difference between b and a is preferably about 0.2mm. For example, b may be 9.8 mm and a may be 9.6 mm.

The bellows 214 has a flange 256 at its open end 252 for fitting intoand engaging with the rebate 227, as shown in FIG. 8.

The function of male end 217 is generally illustrated with respect toFIG. 8. Referring now to FIGS. 11A to 11E, it can be seen that therepresentation of male end 217 in FIG. 8 corresponds to that of FIG.11C. What is not shown in FIG. 8, however, is how outlet fluidcommunication channel 240 communicates with outer chamber 232. This ismore apparent from FIGS. 11A, 11D and 11E, in which it can be seen thatthe male end 217 has flattened side portions 241 where the outlet fluidcommunication channel 240 opens out to the sides of male end 217. Theseflattened side portions 241 allow a small gap between the outside ofmale end 217 and outer wall 212 for providing fluid communicationbetween outlet fluid communication channel 240 (and thus outlet passage231) and outer chamber 232.

Referring now to FIGS. 12A, 12B and 12C, it can be seen that the valvesupport plate 219 is generally disk shaped, but with a center hole 225and additional holes formed toward a periphery of the disk shape so asto provide female end fluid channels 222. A raised portion of the diskacts as the stopper support flange 228 for supporting the outer annularbase of the stopper 221, while the center hole 225 communicates with theconcave interior of the stopper 221. The valve support plate 219 may beheld in place within the outer wall 212 by use of adhesives or may bechemically, ultrasonically or laser welded in place. For additionalsupport, valve support plate 219 may sit against the ends of internalwall ribs 213. This additional support may assist in resisting the forcerequired to be applied to the stopper 221 to open the valve 220. Thevalve support plate 219 and male end 217 are preferably formed of Lexanor Ultem for the autoclavable embodiment or PVC for the non-autoclavableembodiment.

FIG. 13 is an end view of the stopper 221, as if looking toward itthrough the female end opening 226. The stopper head portion 223 andchannel 224 are located centrally on an apex of the stopper 221. Thedepth of channel 224 need only be in the order of 0.5 mm or less, whilethe thickness of the head portion 223 may be in the order of 2 mm. Thediameter of head portion 223 is formed so as to provide only a loose fitwithin female end opening 226 and is not intended to, in itself, occludethe opening.

While certain embodiments have been described above, it is specificallyenvisaged that different parts of the different embodiments may be usedinterchangeably to arrive at further embodiments. For example, thebellows 14, guiding arrangement and indicating mark arrangement shownand described in FIGS. 1, 2 and 5 may be substituted with that describedin relation to FIGS. 8 and 9. Also, the male and female ends shown anddescribed in relation to FIGS. 8, 11A to 11E, 12A to 12C, 13 and 14, maybe used in place of male and female ends 17 and 16 described withreference to FIG. 1. Additionally, autoclavable and non autoclavableversions of each embodiment are envisaged, the difference residing inthe choice of materials for each component. Further, a version of theembodiment shown and described in relation to FIG. 8 is envisaged foruse in a manner similar to that shown and described in relation to FIG.6, such that it is non removably connected to a cuff inflation tube 64of a laryngeal mask 125, such as is shown in FIG. 7.

Another embodiment is similar to that illustrated in FIG. 8 but is madefrom relatively inexpensive material so that it can be made as a singleuse device. The main components of the housing, that is to say the outerwall 212 and the male end 217 is made from transparent polycarbonate.Preferably there are nine ribs in the bellows 214 to provide greateraccuracy and resolution of pressure reading. The bellows 214 is madefrom silicon rubber and the valve stopper 221 is made from siliconrubber. The valve incorporated into the device can be of a type which isin production for other purposes and this reduces manufacturing costs.The part of the housing where the valve is located can be a separatecomponent to allow for easier assembly of the bellows and valvecomponents. The various components can be welded together by using knowntechniques. The overall length of the device 210 is about 60 mm.

Many modifications will be apparent to those skilled in the art. Forinstance, in the previous embodiments the axis of the bellows has beengenerally concentric with the openings 224 and 231. It is possible tovary this.

Referring now to FIG. 15, a further embodiment of the pressureindication device is shown, designated by reference numeral 300. Thisembodiment is similar to the previously described embodiments in manyrespects, including, for example, its functional interaction with thecuff inflation tube and syringe and in having markings on itscylindrical body for facilitating the pressure indication function. Inthis embodiment, the same reference numerals have been used to denoteparts which are the same as or correspond to those of the embodiment ofFIG. 8.

The outer wall 212 forms a generally cylindrical body having a generallyhollow interior 301. Disposed in the interior 301 is the bellows 214.The outer wall 212 and the bellows 214 are generally aligned along alongitudinal axis 303.

The outlet passage 231 defines an axis 305 that is not aligned with thelongitudinal axis 303, and the outlet passage 231 is constituted by theinterior of a hollow spigot 302 which may be welded to or affixed toand/or formed to extend from the outer wall 212. The spigot 302communicates with a port 304. In some embodiments, the spigot 302 iswelded onto the outer wall 212 and is perpendicular thereto. Thegenerally closed end 216 includes the female opening 226. The opening226 defines an axis 307 that is generally aligned with the longitudinalaxis 303.

The closed end 254 of the bellows 214 is biasable along the longitudinalaxis 303 by a fluid in the outer chamber 232. The end chamber 236 of theouter chamber 232 is in fluid communication with the spigot 302 via theport 304. The end chamber 236 communicates through the female end 216 toa syringe when valve 220 is actuated.

The vent passages 230 are formed into an end cap 306 which is welded tothe end of the sidewalls 212. The end cap 306 includes the rebateportion 227 for mounting of the end of the bellows.

In this embodiment, the main components of the housing can be formedfrom transparent polycarbonate and the bellows 214 and valve stopper 221can be made of silicon rubber so that the device is again a single usedevice.

The device 300 shown in FIG. 15 has the advantage that the cuffinflation line 60 is oriented away from the outer wall 212 and bellows214 so that the movement of the bellows 214 tends not to be obscured bythis component. Thus, the movement of the bellows 214 is moreconspicuous to an observer.

FIG. 16 shows a further modified device 310 which operates in a waysimilar to the device 300 shown in FIG. 15. The same reference numeralshave been used to denote parts which are the same as or correspond tothe device 300. In this arrangement, the device 310 includes a generallyhollow body 312 which is separate from the main housing defined by theouter wall 212. The generally hollow body 312 that includes the femaleopening 226. The outlet passage 231 is located or formed within an endcap 314 which is attached to or welded into an open end 313 of the body312. In this embodiment, the axis 305 defined the outlet passage 231 andthe axis 307 defined by the opening 226 are not aligned with thelongitudinal axis 303. The outlet passage 231 and inlet opening 226 maybe concentric and may be perpendicular to the longitudinal axis 303,thereby allowing good visibility of the bellows 214.

The body 312 includes a port 316 which ensures that the internalpressure within the body 232 is the same as that of the outer chamber232. The device 310 is preferably made of the same materials as that ofthe device 300 and is again a single use device. The device is compactand enables ready inspection of expansion and contraction of thebellows.

FIG. 17 illustrates a further modified device 320 which operates in away similar to the device 300 shown in FIG. 15 and/or which operates ina way similar to the device 310 shown in FIG. 16. The same referencenumerals have been used to denote parts which are the same as orcorrespond to those of the device 310.

A difference between this embodiment and the device 310 is that the axis305 of the outlet passage 231 and the axis 307 of the opening 226 aregenerally aligned with the longitudinal axis 303. The vent passages 230are, however, located proximal to the generally closed end 216 andextend generally transversely relative to the longitudinal axis 303through a portion of the outer wall 212. In this arrangement the device320 includes a transverse wall 322 which incorporates the rebate portion227 for mounting of the bellows 214. It will be noted that in thisembodiment the open end of the bellows is oriented towards the opening226.

The device 320 further includes a body 342 that includes the opening226. The body 342 is welded within the outer wall 212 but transfer gaps324 are provided to enable fluid communication from the inlet 226 to theouter chamber 232, as indicated by arrows 326. The body 342 includes thevent passages 230 which, in this embodiment, are angular and communicatewith one or more vent ports 328 for permitting air to pass from theinterior of the bellows 214 to atmosphere when the internal pressure ofthe outer chamber 232 is increased, as before.

The above description of illustrated embodiments, including what isdescribed in the Abstract, is not intended to be exhaustive or to limitthe embodiments to the precise forms disclosed. Although specificembodiments of and examples are described herein for illustrativepurposes, various equivalent modifications can be made without departingfrom the spirit and scope of the disclosure, as will be recognized bythose skilled in the relevant art. The teachings provided herein of thevarious embodiments can be applied to an airway device or facial mask,not necessarily the exemplary laryngeal mask generally described above.

The various embodiments described above can be combined to providefurther embodiments. To the extent that they are not inconsistent withthe specific teachings and definitions herein, all of the U.S. patents,U.S. patent application publications, U.S. patent applications, foreignpatents, foreign patent applications and non-patent publicationsreferred to in this specification and/or listed in the Application DataSheet, including but not limited to U.S. patent application Ser. No.10/515,950, International Application No. PCT/AU03/00634, areincorporated herein by reference, in their entirety. Aspects of theembodiments can be modified, if necessary, to employ systems, circuitsand concepts of the various patents, applications and publications toprovide yet further embodiments.

These and other changes can be made to the embodiments in light of theabove-detailed description. In general, in the following claims, theterms used should not be construed to limit the claims to the specificembodiments disclosed in the specification and the claims, but should beconstrued to include all possible embodiments along with the full scopeof equivalents to which such claims are entitled. Accordingly, theclaims are not limited by the disclosure.

1. A device for indicating internal pressure of an inflatable cuffincluding a housing having: a first opening to which an inflation cufftube can be coupled; a second opening to which a syringe can be coupled;a bellows having an open end in communication with an internal chamber;a cylindrical body portion made of transparent material having means formounting the bellows therein for expansion and contraction in an axialdirection of the bellows; and vents for venting the internal chamber toatmosphere, the arrangement being such that fluid pressure applied bythe syringe in use can cause compression and extension of the bellows tothereby indicate pressure within the housing wherein the axis of thehousing is not aligned with an axis of the first opening or an axis ofthe second opening.
 2. A device as claimed in claim 1 wherein thehousing is hollow.
 3. A device as claimed in claim 2 wherein the housingincludes an integral end formation which includes said second opening.4. A device as claimed in claim 3 wherein the housing includes an endbody which is coupled to the cylindrical body and includes said firstopening, said at least one communication passage and at least one vent,wherein the open end of the bellows is connected to said end body.
 5. Adevice for indicating internal pressure of an inflatable medical cuff,the device including: a body having a first inlet coupling having afirst axis to which a cuff inflation tube can be connected, a secondinlet coupling having a second axis to which a syringe can be connected,the body including a transparent housing which has a cylindrical chamberhaving a third axis therein, the cylindrical chamber being in fluidcommunication with the first and second inlet couplings; and a bellowslocated within the housing and having an internal chamber and beingmounted at one end thereof so that a free end thereof is moveablerelative to third axis in accordance with a pressure differentialbetween the internal chamber and fluid admitted to the body through saidfirst inlet coupling and wherein the third axis is not aligned with bothof said first and second axes.
 6. A device as claimed in claim 5 whereinthe third axis is transverse to the first axis.
 7. A device as claimedin claim 5 wherein the third axis is transverse to the second axis.
 8. Adevice as claimed in claim 5 wherein the body is formed frompolycarbonate and the bellows is formed from silicon rubber.
 9. A deviceas claimed in claim 8 wherein the device is disposable.
 10. A devicethat indicates internal pressure of an inflatable medical cuffincluding: a hollow housing of fixed length having a first generallyclosed end and an opposed second generally closed end and a generallyhollow cylindrical body extending between the opposed generally closedends, the generally hollow cylindrical body is made from transparentmaterial, the hollow housing having a first opening configured to couplewith a cuff inflation tube, a second opening configured to couple with asyringe, and at least one vent extending from an exterior surface of thehollow housing to an interior of the hollow housing, the at least onevent being proximal to the first generally closed end of the pair ofopposed generally closed ends; a valve in the second opening having avalve element which can be unseated from sealing engagement with a valveseat on coupling of the syringe to the second opening for permittinginflating fluid from the syringe to pass into or from the hollowhousing; and a bellows having an outer surface and an open end in fluidcommunication with an inner chamber and a closed end, the bellowsextending into the interior of the hollow housing with the open end ofthe bellows coupled to the hollow housing at the first generally closedend of the pair of opposed generally closed ends, the inner chamber ofthe bellows in fluid communication with an atmosphere that is externalto the device via the at least one vent, wherein an outer chamberextends between the outer surface of the bellows and the hollow housing,and wherein the first opening and the second opening are in fluidcommunication with the outer chamber, whereby in use the outer chamberis at a pressure that is the same as an internal pressure of a cuffcoupled to the first opening, whereby changes in the internal pressureof the cuff cause expansion and retraction of the bellows such that aposition of the closed end of the bellows indicates the internalpressure of the cuff and wherein the generally hollow cylindrical bodydefines a longitudinal axis, wherein the first opening defines a firstaxis, wherein the second opening defines a second axis, and wherein atleast one of the first axis and the second axis is not aligned with thelongitudinal axis.
 11. The device of claim 10 wherein the hollow housinghas at least one fluid communication passage from the first opening tothe outer chamber.
 12. The device of claim 10 wherein at least one ofthe pair of opposed generally closed ends is integral with the generallyhollow cylindrical body of the hollow housing.
 13. The device of claim10 wherein the at least one vent extends through a portion of thegenerally hollow cylindrical body.
 14. The device of claim 10 whereinthe at least one vent extends through a portion of the first generallyclosed end of the pair of opposed generally closed ends.
 15. The deviceof claim 10 wherein the first opening is at the first generally closedend or the second generally closed end of the pair of opposed generallyclosed ends, and wherein the second opening is at the other one of thepair of opposed generally closed ends.
 16. The device of claim 10wherein the first opening and the second opening are at the samegenerally closed end of the pair of opposed generally closed ends. 17.The device of claim 16 wherein the first axis and the second axis arerespectively aligned generally transverse to the longitudinal axis. 18.The device of claim 16 wherein the first axis is aligned generallytransverse to the longitudinal axis, and the second axis is alignedgenerally parallel to the longitudinal axis.
 19. The device of claim 10wherein the generally hollow cylindrical body defines a longitudinalaxis having the bellows generally aligned therewith, wherein the closedend of the bellows is biasable along the longitudinal axis by a fluid inthe outer chamber.